For example, in a solid polymer electrolyte fuel cell, an electrolyte membrane (polymer ion exchange membrane) is interposed between an anode and a cathode to form a membrane electrode assembly (MEA). The membrane electrode assembly is sandwiched between a pair of separators to form a unit cell (power generation cell). In use, in the fuel cell, generally, a predetermined number of unit cells are stacked together to form a fuel cell stack, e.g., mounted in a fuel cell vehicle.
In the fuel cell, a fuel gas flow field is provided in one surface of the separator facing an anode, for supplying a fuel gas to the anode, and an oxygen-containing gas flow field is provided in the other surface of the separator facing a cathode, for supplying an oxygen-containing gas to the cathode. Further, a coolant flow field is formed between the adjacent separators of each fuel cell, for supplying a coolant within an electrode area along surfaces of the separators.
Further, in the fuel cell, so called internal manifold structure is often adopted. In the internal manifold structure, fuel gas passages, oxygen-containing gas passages, and coolant passages extend through the unit cells in the stacking direction for allowing the fuel gas, the oxygen-containing gas, and the coolant to flow through the unit cells.
In this internal manifold type fuel cell, seals need to be provided in an air-tight manner or a liquid-tight manner for preventing leakage of the fuel gas, the oxygen-containing gas, and the coolant. In this regard, for example, a method for fabricating a seal-integrated separator disclosed in Japanese Patent No. 3532547 is known.
In this production method, a separator body is held between an upper mold and a lower mold. In this state, melted seal material is injected into each of grooves in the upper mold and the lower mold through separate gates, respectively, to form the seal material integrally and simultaneously on both surfaces of the separator body. Therefore, according to the disclosure, in comparison with the case of providing seal material separate from the separator body on both front and back surfaces of the separator body and the case of coating the seal material on the separator body, the seal material can be positioned highly accurately, and the number of assembling steps is reduced greatly.